A vehicle perimeter monitor displays an image shot by a camera in order to improve an eyesight of a driver of the vehicle. In JP-A-2005-110202 corresponding to US 2005/0083405, the vehicle perimeter monitor includes a camera device having a wide lens, of which a field angle is equal to or larger than 180 degrees. Although the camera device can shoots an image in a wide sight range, as shown in FIG. 3, an object on a periphery of the image has a twist image, which is comparatively small. Specifically, when the driver backs the vehicle, it is necessary for the driver to pay attention to a clearance between the vehicle and an adjacent vehicle, which is parked next to the vehicle. Thus, the driver may not recognize the object, which is displayed small on the display screen.
Accordingly, for example, JP-A-2005-123968 teaches a monitor such that the monitor retrieves an image of a moving object from a shot image, and emphasizes and displays the image of the moving object. The monitor calculates an optical flow of a characteristic point of the shot image so that a moving vector of each characteristic point is obtained. Thus, the monitor can retrieve the image of the moving object. When the retrieved image of the moving object is emphasized and displayed, the driver of the vehicle can recognize easily that the moving object exists at a blind area in front of the vehicle.
However, an image processing for retrieving the moving vector with using the optical flow needs a huge amount of calculation. Accordingly, it is necessary to add a dedicated processor for reducing a process time when the image of the moving object is retrieved with high accuracy with following the movement of the moving object.